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static void X(String a,String b,String c)
{
TextBox textBox3 = new TextBox();
a = textBox3.Text;
if (a == " ")
{
throw new ArgumentNullException(a);
}
TextBox textBox4 = new TextBox();
b = textBox4.Text;
if (b == null)
{
throw new ArgumentNullException(b);
}
TextBox textBox5 = new TextBox();
c = textBox5.Text;
if (c == null)
{
throw new ArgumentNullException(c);
}
}
private void Go2_Click(object sender, EventArgs e)
{
try
{
........//my code
X(Sx,Sy,V);
........// my some code
}
catch (System.ArgumentNullException)
{
MessageBox.Show("Your String is not correct");
}
}
My program cannot do System.ArgumentNullException. How can I solve this program?Please, guide.
You need to use the string.IsNullOrEmpty() to check the values for your string variables. As you are assigning them values in your method using textbox.Text. They get the string.Empty values assigned to them. And Your if statements never evolves to true and they never throw the exception.
If you alter your conditions like this then that would work,
if (string.IsNullOrWhiteSpace(a))
{
throw new ArgumentNullException("Thrown from first condition");
}
to check if a string is null use the dedicated functions for this and initialize the ArgumentNullException with the parameter name and not with the parameter.
For example instead of
if (a == " ")
{
throw new ArgumentNullException(a);
}
write
if (string.IsNullOrWhiteSpace(a))
{
throw new ArgumentNullException("a");
}
for
if (c == null)
{
throw new ArgumentNullException(c);
}
write
if (string.IsNullOrEmpty(c))
{
throw new ArgumentNullException("c");
}
Try instead of :
throw new ArgumentNullException(c);
catch (System.ArgumentNullException)
{
MessageBox.Show("Your String is not correct");
}
This :
throw new ArgumentNullException("Your String is not correct");
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
Related
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Closed yesterday.
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I need some help please. I need to remove dublicates and use regex when load a list of email adresses in datagrid. Regex must check for syntax email adress to be correct.
Here is my code:
public void StoreEmailToDataGrid(string filePath, DataGridView dataGridView)
{
try
{
var baca = File.ReadLines(filePath);
foreach (var line in baca)
{
var rowIndex = dataGridView.Rows.Add();
dataGridView.Rows[rowIndex].Cells[0].Value = rowIndex + 1;
dataGridView.Rows[rowIndex].Cells[1].Value = line;
}
this.totalRows = dataGridView.Rows.Count;
}
catch (IOException)
{
}
}
private void buttonImportMailist_Click(object sender, EventArgs e)
{
string file = "";
openFileDialog1.Filter = "Text Files|*.txt";
openFileDialog1.Title = "Select Mailist";
openFileDialog1.FileName = file;
DialogResult result = openFileDialog1.ShowDialog(); // Show the dialog.
if (result == DialogResult.OK) // Test result.
{
file = openFileDialog1.FileName;
try
{
email.StoreEmailToDataGrid(file, dataMailist);
}
catch (IOException)
{
MessageBox.Show(result.ToString());
}
}
}
UPD: Remove dublicates solved
var baca = File.ReadLines(filePath).Distinct().ToArray()
Remain, how to use regex to check correct email adresses.
Solved the problem. Just use regex.ismatch
Regex.IsMatch(strIn, #"^([\w-.]+)#(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.)|(([\w-]+.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(]?)$");
IN WPF project, whenever I try to add selected Student in selected university and display it on assoiated table.
Here is image of my table -
https://i.stack.imgur.com/KUHuF.png
I encounter this problem, once I hit update assosiated button.
public System.Data.Linq.Table<Student> Students
{
get
{
return this.GetTable<Student>();
}
}
The above code is in "Dataclasses1.designer.cs" window.
However, upon restarting the program, selected student is sucessfully added to selected university.
Here is my code -
private void UpdateAssociatedStudent_Click(object sender, RoutedEventArgs e)
{
if(ListUniversity.SelectedItem != null || ListStudent.SelectedItem != null)
{
using (dataContext = new DataClasses1DataContext())
{
UniversityManager universityManager = new UniversityManager
{
UniFK = int.Parse(ListUniversity.SelectedValue.ToString()),
StdFK = int.Parse(ListStudent.SelectedValue.ToString())
};
dataContext.UniversityManagers.InsertOnSubmit(universityManager);
dataContext.SubmitChanges();
}
ShowAssociatedStudents();
Sucess.Text = "Student is sucessfully added to University";
}
}
Edit - Adding image for error
https://i.stack.imgur.com/ApPxd.png
I think that you may need to change this line of code:
if(ListUniversity.SelectedItem != null || ListStudent.SelectedItem != null)
to
if(ListUniversity.SelectedItem != null && ListStudent.SelectedItem != null)
I've solved this issue by running try/catch instead of using 'Using' statement. my edited code looks like this.
//Add selected student from selected university in associated student listbox
private void UpdateAssociatedStudent_Click(object sender, RoutedEventArgs e)
{
if(ListUniversity.SelectedItem != null && ListStudent.SelectedItem != null)
{
try
{
uniManager = new UniversityManager()
{
UniFK = Convert.ToInt32(ListUniversity.SelectedValue),
StdFK = Convert.ToInt32(ListStudent.SelectedValue)
//UniFK = int.Parse(ListUniversity.SelectedItem.ToString()),
//StdFK = int.Parse(ListStudent.SelectedItem.ToString())
};
dataContext.UniversityManagers.InsertOnSubmit(uniManager);
dataContext.SubmitChanges();
ShowAssociatedStudents();
}
catch (FileNotFoundException)
{
Console.WriteLine("File Not Found.");
}
catch (OutOfMemoryException)
{
Console.WriteLine("Out of Memory.");
}
catch (IOException)
{
Console.WriteLine("An I/O error has occured.");
}
}
else
{
Failed.Text = "Please select the missing items from either university or student.";
}
}
Hope you all well. I would like to ask you for an advise.
I am looking for a way to validate a data before OnClick button gets executed.
I do have few ComboBoxes with some data to choose from. Currently I have used some solution, which does look quite "dirty" and I am not happy about it.
Currently I am using something similar to this:
if(box1 == null)
{
MessageBox.Show("Error 1");
}
if(box2 == null)
{
MessageBox.Show("Error 2");
}
if(box3 == null)
{
MessageBox.Show("Error 3");
}
If I am having 3 fields empty I will get message displayed 3 times one for each error. Is there a way to list all errors within one message box if error is true?
I was thinking of something like this:
bool a = true;
bool b = true;
bool c = true;
a = (box1 == null);
b = (box2 == null);
c = (box3 == null);
if(a || b || c)
{
//Display list of errors where condition is true
}
I would highly appreciate any suggestions.
Many thanks in advance.
Something like this:
var errors = new List<string>();
if(box1 == null)
errors.Add("Error 1");
if(box2 == null)
errors.Add("Error 2");
if(box3 == null)
errors.Add("Error 3");
if (errors.Count > 0)
MessageBox.Show(string.Join(Environment.NewLine, errors));
Use String builder for this String builder
private object box1;
private object box2;
private object box3;
//The following code base could be in a button click event
StringBuilder errorMessages = new StringBuilder();
if(box1 == null)
{
errorMessages.AppendLine("Error 1");
}
if(box2 == null)
{
errorMessages.AppendLine("Error 2");
}
if(box3 == null)
{
errorMessages.AppendLine("Error 3");
}
if(!string.IsNullOrWhiteSpace(Convert.ToString(errorMessages)))
{
MessageBox.Show(errorMessages.ToString(), "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning);
}
In my project I'm trying to write code that will be nice to understand.
I currently split my data access functions in a seperate class.
What I'm trying to achieve however, is to catch the errors back to my form. I am not getting this currently and I was wondering why.
In my form I have the following code:
private void btn_Save_ItemClick(object sender, ItemClickEventArgs e)
{
if (dal.updatePerson(ObjectAfterSaving))
{
MessageBox.Show("Updated!");
}
else
{
MessageBox.Show("error");
};
}
In my dal object (derived from the DataAccess_Person class), I have the following method:
public bool updatePerson(Person p)
{
conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["Database"].ConnectionString);
SqlCommand command = new SqlCommand(#"UPDATE Person
SET PersonName = #PersonName
WHERE PersonID = #PersonID", conn);
command.Parameters.Add("#PersonName", SqlDbType.VarChar).Value = p.Name
{
try
{
if (conn.State == ConnectionState.Closed)
{
conn.Open();
}
int a = command.ExecuteNonQuery();
conn.Close();
if (a > 0)
{
return true;
}
else
{
return false;
}
}
catch (SqlException ex)
{
ex.ToString();
return false;
}
}
}
My question is: let's say if my method falls in the catch. Will my front end (form) show it (Sql Exception for example) ? Or will i just get 'error' ? And If I will just get error, how I can improve my code to show the Exception instead of error?
A simple way is to remove the try catch from your DAL and add it to the form. For example:
private void btn_Save_ItemClick(object sender, ItemClickEventArgs e)
{
var result = "Success";
try
{
dal.updatePerson(ObjectAfterSaving);
}
catch (SqlException sqlEx)
{
result = sqlEx.Message;
}
catch (Exception ex)
{
result = ex.Message;
}
MessageBox.Show(result);
}
Just note that there's a lot of ways you can do this. My preference is to not include DAL specific exception types in my UI. Instead I may return a custom result type that has an errorcode and message and let my UI display that or generate a custom message based on the error code.
You‘ll just get „error“ in case of a SqlException. All other exceptions will crash your program if you don‘t have a global exception handler. If you want to show the error message you could introduce an out variable for the error message:
bool successful = MyMethod(out string errorMessage)
if (!successful)
{
MessageBox.Show(errorMessage);
}
public bool MyMethod(out string errorMessage)
{
errorMessage = "";
try
{
// do some stuff
return true;
}
catch(Exception ex)
{
errorMessage = ex.Message;
return false;
}
}
I have a subroutine. It comapares whether values are empty then doing something. For example, if they are empty, then warnings are raised.
The code works fine. But when value are not empty, the warnings are still pop out. Please help me to correct the logic.
Thanks.
private void btnNew_Click(object sender, EventArgs e)
{
try
{
if (txtbox1.Text.ToString().Trim() == string.Empty)
{
goto Msg1;
}
if (txtbox2.Text.ToString().Trim() == string.Empty)
{
goto Msg2;
}
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = txtbox1.Text;
dr["Abbr"] = txtbox2.Text;
dr["SortOrder"] = Convert.ToDecimal(numericOrder.Value);
if (SortOrders.Contains((decimal)dr["SortOrder"]))
{
goto Msg3;
}
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
Msg1:
MessageBox.Show("Description is required.");
Msg2:
MessageBox.Show("Abbr is required.");
Msg3:
MessageBox.Show("Please select another one, this one is already used.");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
From the above code, you see. if txtbox1 has some value, the program still displays Msg1. I want to avoid it.
Because labels are just labels, and code after them is executed sequentially.
Why can't you do just this:
try
{
if (txtbox1.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Description is required.");
return;
}
if (txtbox2.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Abbr is required.");
return;
}
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = txtbox1.Text;
dr["Abbr"] = txtbox2.Text;
dr["SortOrder"] = Convert.ToDecimal(numericOrder.Value);
if (SortOrders.Contains((decimal)dr["SortOrder"]))
{
MessageBox.Show("Please select another one, this one is already used.");
return;
}
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
It's so much more readable.
Restructure your code to avoid goto - it is a relic and not much use in a properly object oriented codebase.
Returning from the method, throwing exceptions or building an errors dictionary are all better options than using goto.
For example, you can have a List<string> errors which you add to when you get an error condition.
If it is empty, no errors were encountered, if it isn't, there were.
This is a good case were goto is the wrong way to go. Use something like this instead.
private void btnNew_Click(object sender, EventArgs e)
{
try
{
bool error = false;
if (txtbox1.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Description is required.");
error = true;
}
if (txtbox2.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Abbr is required.");
error = true;
}
if (SortOrders.Contains(Convert.ToDecimal(numericOrder.Value)
{
MessageBox.Show("Please select another one, this one is already used.");
error = true;
}
if(error)
return;
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = txtbox1.Text;
dr["Abbr"] = txtbox2.Text;
dr["SortOrder"] = Convert.ToDecimal(numericOrder.Value);
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
Edit
Just figured that my code didn't actually do the same as his first sample since it only displayed the first error no matter how many that occured. Updated my sample to accomodate for that.
I've always been taught to avoid goto like the plague, and it's something I've followed for years. I've never even considered it to be an option when writing code.
Thinking about it though, I did read an article a few years ago (which I can't find now) which said you could credibly use gotos only if you used it to jump down code, and not up: a rule that is stuck to here.
Check here for more info: Does anyone still use [goto] in C# and if so why?
There are better ways of using goto statement, for instacne using "return" (when used in the middle of a method), "break" and "continue". Have you ever used one of these?
private void btnNew_Click(object sender, EventArgs e)
{
try
{
var description = txtbox1.Text.Trim();
if (string.IsNullOrEmpty(description))
{
MessageBox.Show("Description is required.");
return;
}
var abbr = txtbox2.Text.Trim();
if (string.IsNullOrEmpty(abbr))
{
MessageBox.Show("Abbr is required.");
return;
}
var numericOrderValue = Convert.ToDecimal(numericOrder.Value);
if (SortOrders.Contains(numericOrderValue)
{
MessageBox.Show("Please select another one, this one is already used.");
return;
}
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = description;
dr["Abbr"] = abbr;
dr["SortOrder"] = numericOrderValue;
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void btnNew_Click(object sender, EventArgs e)
{
try
{
if (txtbox1.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Description is required.");
}
if (txtbox2.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Abbr is required.");
}
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = txtbox1.Text;
dr["Abbr"] = txtbox2.Text;
dr["SortOrder"] = Convert.ToDecimal(numericOrder.Value);
if (SortOrders.Contains((decimal)dr["SortOrder"]))
{
MessageBox.Show("Please select another one, this one is already used.");
}
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
Try this. It works.